Interplay of Ultrafast Electron-Phonon and Electron-Electron Scattering in Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> MXenes: Ab Initio Quantum Dynamics.
basic_science · Level V
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- Record sourced from PubMed, PMID 40272202.
- Also identified by DOI 10.1021/acs.nanolett.5c01242.
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Abstract
Nonthermal electrons are vital in solar energy and optoelectronics, yet their relaxation pathways are not fully understood. Ab initio quantum dynamics reveal that in Ti<sub>3</sub>C<sub>2</sub>O<sub>2</sub> electron-phonon (e-ph) relaxation is faster than electron-electron (e-e) scattering due to strong coupling with the A<sub>1g</sub> phonon at 190 cm<sup>-1</sup> and the presence of light C and O atoms. Nuclear quantum effects are minimal; vibrations influence e-e scattering only indirectly, and the A<sub>1g</sub> mode' zero-point energy is much lower than thermal energy at ambient conditions. Substituting O with heavier S in Ti<sub>3</sub>C<sub>2</sub>OS slows e-ph relaxation and enhances e-e scattering, making it a faster process. However, both channels proceed concurrently, challenging the e-e and e-ph time scale separation often used for metals. These results underscore the need for atomistic-level understanding of nonthermal electron dynamics, especially in light-element systems such as MXenes, and provide guidance for optimizing electronic relaxation in advanced optoelectronic materials and devices.